/Engine/Plugins/FX/Niagara/Source/Niagara/Public/NiagaraParameterBinding.h
Binding usage flags Note that Emitter / Particle bindings are only allowed if the binding variable is outered to aUNiagaraEmitter
enum ENiagaraParameterBindingUsage { User = 1 << 0, System = 1 << 1, Emitter = 1 << 2, Particle = 1 << 3, StaticVariable = 1 << 4, NotParticle = StaticVariable | User | System | Emitter, All = StaticVariable | User | System | Emitter | Particle, }